On August 4, 2002, about 1800 Alaska daylight time, a Piper PA-18-150 airplane, N4151Z, sustained substantial damage following a loss of control and in-flight collision with terrain after takeoff from the Gulkana Airport, Gulkana, Alaska. The airplane was being operated as a visual flight rules (VFR) personal flight under Title 14, CFR Part 91, when the accident occurred. The private pilot and sole passenger were not injured. Visual meteorological conditions prevailed, and no flight plan was filed. The flight originated at the McCarthy Airport, McCarthy, Alaska, about 1600, and was bound for Lake Hood Strip, Anchorage, Alaska, with a fuel stop at Gulkana. During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) on August 8, the pilot said he refueled the accident airplane at Gulkana, and prepared for departure. He said he and his passenger had some camping gear and food in the airplane, but they were well within the gross weight limitation of the airplane. He said it was hot, and the airport was reporting a density altitude of 3,500 feet. He chose to takeoff on the 2,100 foot gravel runway rather then the 5,000 foot paved runway, since the airplane was tundra tire-equipped. He said the winds were reported as light and variable, and that he held the airplane on the ground until his hand-held global positioning system (GPS) indicated a ground speed of 51 knots, and then lifted off. About 70 feet above ground level, he said he started a shallow left turn. He said as he rolled the airplane into the turn it started to descend, and he tried to level the wings. He said the control stick was jammed, and would not return to neutral. The airplane continued its descent, impacting the ground in a left turn. Both wings and fuselage sustained substantial damage. The pilot reported that the flight from McCarthy to Gulkana was uneventful, and that the airplane's engine was developing full power during takeoff at Gulkana. He further stated there were no known mechanical anomalies with the airplane prior to the accident. A postaccident examination by the pilot of the airplane's control system failed to disclose the reason for the control stick jam.